Process for the manufacture of omicron, omicron-dialkylthiono-phosphoric acid chlorides



United States Patent Ofiice 3,356,774 Patented Dec. 5, 1967 3,356,774PROCESS FOR THE MANUFACTURE OF 0,8-DIAL- KYLTHIONO-PHOSPHGRIC ACIDCHLORIDES Hermann Niermanu, Bruhl, near Cologne, Joseph Cremer,Hermulheinr, near Cologne, and Heinz Harnisch, Lovenich, near Cologne,Germany, assignors to Knapsack-Griesheim Aktiengesellschaft, Knapsack,near Cologne, Germany, a corporation of Germany No Drawing. Filed Aug.27, 1964, Ser. No. 392,611 Claims priority, application Germany, Sept.13, 1963, K 50,811; July 24, 1964, K 53,557 15 Claims. (Cl. 260981) Thepresent invention is concerned with a process for the manufacture of0,0-dialkylthionophosphoric acid chlorides having the general formula:

in which R stands for an alkyl radical having 1 to 6 carbon atoms.

It is known that 0,0-diethylthionophosphoric acid chloride can beprepared by a two step process wherein, in a first process step,phosphorus pentasulfide is caused to react with ethanol according to thefollowing equation:

so as to form 0,0-diethyldithiophosphoric acid and hydrogen sulfide andwherein, in a second process step, the isolated0,0-diethyldithiophosphoric acid is chlorinated in an appropriatesolvent with ch orine gas according to the following equation:

2(C2H50)2P(S)SH 3012 2(C2H5O)2P(S)Cl 21101 S2012 the chlorinatingreaction resulting in the formation of 0,0-diethylthionophosphoric acidchloride.

The 0,0-diethylthionophosphoric acid chloride prepared in conventionalmanner is obtained with a maximum yield of 70%, related to the amount of0,0-diethyldithiophosphoric acid obtained in the first process step.

This conventional method is beset with various disadvantages. Firstly,the hydrogen sulfide formed in the first process step as a by-productmust be rendered harmless by specific means. Secondly, the work-up ofthe disulfur dichloride obtained in the second process step is difficultto achieve and expensive. Thirdly, the chlorination reaction accordingto Equation II is strongly exothermal and sometimes proceeds inexplosion-like manner, so that care must always be taken to ensure goodcooling of the reaction mixture.

The present invention obviates the above disadvantages by providing aprocess wherein the work-up of resulting by-products and special coolingof the reaction mixture may be omitted. Furthermore, the process iscarried out in a single step with the use of a readily available andcommercially cheap starting product.

The process of the present invention for making 0,0-dialkylthionophosphoric acid chlorides having the general formula:

ROl OR 51 in which R stands for an alkyl radical having 1 to 6 carbonatoms is basically carried out according to the following reactionequation:

(III) P S +.4ROH+3Cl 2(RO) P(S)Cl+6HCl-|-3S The process of the presentinvention comprises introducing a stream of chlorine gas into a P S-suspension in an inert solvent at a temperature within the range ofabout 0 to 150 C. and adding dropwise concurrently therewith an alcoholhaving 1 to 6 carbon atoms, allowing the reaction to proceed tocompletion, expelling the solvent, and isolating0,0-dialkylthionophosphoric acid chloride from the reaction mixture bysubjecting it to distillation.

In determining the reaction conditions applicable to the process of thepresent invention it has been found advantageous to react the phosphoruspentasulfide serving as the feed with a suitable alcohol and chlorinegas in a definite molar ratio of 1:40 to 4.4:2.2 to 3.2. The proportionof chlorine used, i.e. 2.2 to 3.2 mols per mol phosphorus pentasulfide,is especially important since outside this range the yield of0,0-clialkylthionophosphoric acid chlorides will drop. For making0,0dimethylthionophosphoric acid chloride, for example, the P 8 alcoholand chlorine should be used in a molar ratio of 124.0 to 4.4:2.2 to 2.7,preferably of 1:4.4:2.4.

It has also been found that the yield of 0,0-dialkylthionophosphoricacid chlorides is influenced by the proportion of alcohol and chlorineadded per unit of time to the phosphorus pentasulfide suspension.Maximum yields are obtained by adding the chlorine gas to the phosphoruspentasulfide suspension in an inert solvent in such a way that abouthalf of the calculated chlorine quantity has been introduced thereintoonce the total amount of alcohol has been added. In other words,chlorine and alcohol are introduced at a feed rate or speed ofapproximately 1:2. The balance chlorine portion is then introducedcontinuously at a constant feed rate into the suspension. Introductionof the chlorine gas either after the addition of the total amount ofalcohol or at a feed rate the same as the alcohol will result in reducedyields.

It has also been found that the yields are a function of the temperatureused in the process of the present invention, i.e. that by maintaining areaction temperature of about 70 to C. within the interesting range ofabout 0 to C. is most advantageous.

A further feature of the present invention resides in the use of aninert solvent for making the necessary phosphorus pentasulfidesuspension. The inert solvents useful for this include e.g. toluene,xylene, carbon tetrachloride, petroleum ether (B.P.: 6595 C.) or thelike as well as the 0,0-dialkylthionophosphoric acid chloride obtainedas the reaction product.

The alcohols useful for use in carrying out the process of the presentinvention include e.g. methanol, ethanol, propanol, iso-propanol,n-butanol, iso-butanol, amyl alcohol, hexyl alcohol and the isomersthereof.

The process of the present invention is generally carried out bycharging an appropriate reaction vessel with approximately equal partsby weight of phosphorus pentasulfide and inert solvent, stirring thematerial in the vessel so as to obtain a suspension, gradually admixingthe suspension with a suitable alcohol and chlorine gas, the chlorinegas being introduced in such a way that about half of the calculatedchlorine quantity has undergone reaction once the total amount ofalcohol has been added to the suspension. The chlorine balance portionis introduced subsequent to the alcohol addition while maintaining theinitial rate of flow. During the entire reaction time, the reactiontemperature is maintained e.g. at 70 C. by slight heating or slightcooling as the case may be. Once the chlorine addition has beenterminated, the reaction mixture is first freed from the inert solvent,and 0,0-dialkylthionophosphoric acid chloride is then distilled off,preferably under reduced pressure. During such treatment, thetemperature in the sump portion of the reaction vessel may increase toabout 150 C. The remaining 3 liquid sump phase solidifies on cooling andconsists substantially of elementary sulfur.

It has also unexpectedly been found that the yields can be furtherimproved by introducing into the reaction mixture diluted chlorine gas,i.e. chlorine gas in admixture with an inert gas, e.g. carbon dioxideand argon, preferably nitrogen, in a ratio by volume of about 1:05 to1:3.

Still further, it has proved advantageous to use about 1 to 2 liters,preferably 1.5 liters solvent per kg. P S

In contrast to the art holding 0,0-dialkylthionophosphoric acidchloridesto undergo explosion-like reaction with water at 60 C., it has beenfound that these compounds can be purified without undergoingdecomposition in easy and harmless manner by being subjected to steamdistillation.

The process of the present invention taken as a whole offers a series ofcharacteristic advantages over customary methods. Firstly, it enablesthe desired process product to be prepared in a single process step, thenecessary feed product being readily available and relatively cheap.Secondly, the reaction of the phosphorus pentasulfide with alcohol andchlorine gas is but slightly exothermal and therefore requires nocooling. steps in the absence of any danger of explosion. Furthermore,any expensive work-up or destruction of by-products is obviated becausethe sulfur obtained as the distillation residue is useful for furtherapplication. Still further, the dialkylthionophosphoric acid chlorideprepared by the process of the present invention is obtained in yieldsof more than'90%, related to the dialkyldithiophosphoric acid formed asan intermediary product, i.e. in yields considerably higher than thoseobtained by conventional methods.

The following examples serve to illustrate the invention, but they arenot intended to limit it thereto:

Example 1 1.11 kg. phosphorus pentasulfide were suspended while stirringin 1 liter toluene which had beenplaced into a 4-liter four-neckedflask, and the suspension was admixed within 100 minutes with 1,285liters ethanol and 532 grams, i.e. the half of the necessary chlorinegas. Once the alcohol had been added, a further 532 grams chlorine gaswere caused to react with the phosphorus pentasulflde which hadmeanwhile dissolved. During the whole reaction time, the temperature wasmaintained at 70 C. by slight heating or slight cooling. After thechlorine had been added, the toluene was expelled from the reactionmixture and diethylthionophosphoric acid chloride was distilled off at68 C. and under a pressure of 8 mm. mercury. The remaining liquiddistillation residue was first heated at a sump temperature of 150 C.,then cooled and the residue which consisted substantially of elementarysulfur was allowed to solidify.

1360 grams diethylthionophosphoric acid chloride having a refractiveindex of n =1.4690 were obtained corresponding to a yield of 73%,calculated on the amount of phosphorus pentasulfide used. The productobtained had a degree of purity of 99.3% as determined bygaschromatographic analysis.

Example 2 In a manner analogous to that described in Example 1, 222grams phosphorus pentasulfide were suspended while stirring in 194 cc.toluene placed in a 1-liter four-necked round flask, and the suspensionwas admixed in the course of 100 minutes with 187 cc. methanol. Duringthe methanol addition, 107 grams chlorine gas were introduced followedby the introduction of a further 107 grams chlorine gas during a further100 minutes period of time. During the reaction, the reactiontemperature was at about 70 C. After the necessary amount of chlorinegas had been introduced, the toluene was expelled from the reactionmixture and dimethylthionophosphoric acid chloride was distilled offunder a pressure of 16 mm. mercury at a temperature of 61 C. 210 gramsdimethylthionophosphoric acid chloride were obtained, corresponding to ayield of 65% related to the amount of phosphorus pentasulfide used. Theproduct so prepared had a refractive index of 11 14805.

Example 3 and dibutylthionophosphoric acid chloride was distilled off ata pressure of 5 mm. mercury at a boiling temperature of 107 C. 293 gramsdibutylthionophosphoric acid chloride were obtained. This correspondedto a yield of 60% related to the amount of phosphorus pentasulfide used.The product so prepared had a refractive index of n =l.467O.

Example 4 The apparatus was a 20-1iter glass flask provided with astirring means and 4 inlet sockets, of which each socket was intendedrespectively to serve as methanol supply, gas admission, refluxcondenser and temperature determination. The reflux condenser had aninternal width of mm. and was packed over a length of 1 meter withsaddle-shaped packing material. The gas admission line was a T-pieceserving to supply chlorine and nitrogen. The glass flask was placed in ametal trough having joints for supplying cooling water and hot steam.5.55 kg. P 5 were suspended while stirring in 7.8 liters CCL; in theflask and 4.45 liters CH OH were added. At the start of the reaction,the flask had to be cooled with some water. The reaction material wasmaintained at a temperature of 40 to 50 C. and a mixture of 350 l./hr.C1 and 350 l./hr. N was introduced thereinto. The chlorine was used in aproportion corresponding to a molar ratio of P2S5:Cl2 1I2.5.

After the chlorine addition, the hydrogen chloride appearing in thereaction product was expelled with nitrogen in the course of 30 minutes.

The above batch gave 15.385 kg. reaction sump. An aliquot portion of1.381 kg. was distilled. 360 grams yellow-colored CCl were withdrawn ata temperature of 60 to 70 C. in the still portion and under, a pressureof 2080 mm. mercury. 598 grams yellow-colored crude product wereobtained under reduced pressure of 5 mm. mercury and a maximum stilltemperature of 110 C. The crude product was hydrolyzed for /2 hour with200 cc. water at 30 C. and then separated in a separating funnel intotwo phases. The lower phase (533 grams) was again rectified underreduced pressure. 535 grams pure 0,0-dirnethylthionophosphoric acidchloride were obtained. Calculated on the whole batch, this correspondedto a 74.5% yield of 0,0-dimethylthionophosphoric acid chloride, relatedto P 5 The crude product can be hydrolyzed and purified in a single stepby subjecting it to steam distillation. In this case, the final product,i.e. the acid chloride, was again obtained in the form of a clear,water-white liquid.

We claim:

1. A process for the manufacture of 0,0-dialkylthionophosphoric acidchlorides having the general formula:

in which R stands for an alkyl radical having 1 to 6 carbon atoms, whichcomprises reacting a phosphorus pentasulfide suspension in an inertsolvent at a temperature within the range of about 0 to C. with chlorineand an alcohol having 1 to 6 carbon atoms by introducing a stream ofchlorine into the said suspension and adding dropwise concurrentlytherewith the alcohol, allowing the chlorinating reaction to proceed tocompletion, expelling the said solvent from the resulting reactionmixture and isolating 0,0-dialkylthionophosphoric acid chloride bydistillation.

2. A process as claimed in claim 1, wherein the inert solvent is atleast one member selected from the group consisting of toluene, xylene,carbon tetrachloride, a pctroleum ether having a boiling point of 65 to95 C., and the 0,0-dialkylthionophosphoric acid chloride obtained as thefinal product.

3. A process as claimed in claim 1, wherein phosphorus pentasulfide isreacted with the alcohol and the chlorine gas in the molar ratio of1:4.0 to 4.4222 to 3.2.

4. A process as claimed in claim 3, wherein the phosphorus pentasulfide,the alcohol and the chlorine are used in a molar ratio of 1:4.0 to4.4:2.2 to 2.7 so as to prepare 0,0-dimethylthionophosp'horic acidchloride.

5. A process as claimed in claim 4, wherein the molar ratio of P S:alc0hol:chlorine amounts to 1:4.4:2.4.

6. A process as claimed in claim 1, wherein the phosphorus pentasulfideis reacted with the alcohol and the chlorine gas at a temperature withinthe range of about 70 to 90 C.

7. A process as claimed in claim 1, wherein the phosphorus pentasulfidesuspension in the inert solvent is admixed with the chlorine gas and thealcohol at a feed rate of approximately 1:2.

8. A process as claimed in claim 1, wherein the phosphorus pentasulfideand the inert solvent are used in about equal parts by weight.

9. A process as claimed in claim 8, wherein about 1 to 2 liters solventare used per kg. P 8

10. A process as claimed in claim 9, wherein 1.5 liter solvent isemployed per kg. P 8

11. A process as claimed in claim 1, wherein chlorine gas diluted withan inert gas is introduced into the reaction mixture.

12. A process as claimed in claim 11, wherein the inert gas is at leastone member selected from the group consisting of nitrogen, carbondioxide and argon.

13. A process as claimed in claim 11, wherein the chlorine gas is mixedwith the inert gas in a ratio by volume of 1:05 to 1:3.

14. A process as claimed in claim 1, wherein the 0,0-dialkylthionophosphoric acid chloride is isolated from the reactionmixture by distillation under reduced pressure.

15. A process as claimed in claim 1, wherein the fiinal product obtainedis purified by being subjected to steam distillation.

References Cited FOREIGN PATENTS 1,211,170 2/1966 Germany.

CHARLES B. PARKER, Primary Examiner.

A. H. SUTTO, Assistant Examiner.

1. A PROCESS FOR THE MANUFACTURE OF O,O-DIALKYLTHIONOPHOSPHORIC ACIDCHLORIDES HAVING THE GENERAL FORMULA: